Photo-oscillator-modulator system



AU Z33 EX RES-601 Dec. 25, 1934. A. MOI... NICOLSON PHQTO OSCILLATOR MODULATOR SYSTEM Filed Oct. 17, 1950 2 Sheets-Sheet 1 9v mw Ll E R. IN LI k ,nw NI mlwnm w w QM PllLillbllilllIllllK mfi W W. W mm A Filed Oct. 17, 1930 2 Sheets-Sheet 2 l NVENTOR A/exander M Lean Nico/5m UM/FWM ATTORNEY we... .1 e.

Patented Dec. 25, 1934 UNITED STATES PATENT OFFICE PHOTO-OSGILLATOR-MODULATOR SYSTEM Application October 1'7, 1930, Serial No. 489,348

9 Claims.

This invention relates to the generation of electrical oscillations, and particularly to the generation of electrical oscillations and their modulation by signal variations.

An object of this invention is to generate electrical oscillations utilizing a photosensitive medium and light path.

Another object of the invention is to generate electrical oscillations, a portion of the circuit being a light path which serves as a modulating medium.

A further object of the invention is to generate electrical oscillations by utilizing a wave retardation circuit in the electrical portion of a photoelectric circuit.

It is well known in the art how to generate electrical oscillations by means of a triode vacuum tube, in which system the output of the tube is connected to the input to feed back a certain proportion of the output energy to regenerate and sustain the oscillations. It is also well lmown how electrical vibrations may be created by mechani cal generating apparatus such as mechanical vibrators and the like.

In the present invention, however, the action of a varying light beam in accordance with the oscillations to be generated, are directed on a photoelectric cell device. After amplification within the device or with external amplifiers, the varying light beam is again created from energy released by the light variations. Within the electrical portion of the circuit is a wave retardation or delay circuit which slows up the transmission therethrough of the wave in accordance with its constants and depending upon the frequency desired to be generated. This delay circuit is adjustable, permitting different frequencies to be obtained. A particular feature of this invention is the use of a compound photoelectric cell amplifier as a unitary structure within a single evacuated envelope. This device has a light sensitive cathode directly connected to the control electrode of the vacuum tube, while the filament thereof serves as the anode of the photocell combination. With this arrangement, therefore, a considerable amount of output potential may be obtained without the use of an external amplifier. Furthermore, with the present oscillating system, a plurality of various oscillations may be generated. employing the same light path and photoelectric cell system to provide a compound generator.

The oscillator-modulator system disclosed below is the above mentioned photo-electrical oscillator circuit which is modulated by varying the light path, in accordance with the signal variations. That is, an auxiliary source of light is provided which varies in accordance with the signals to be transmitted along the light channel provided for the carrier frequencies.

The invention will be more fully understood from the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic circuit of a compound oscillating system; and,

Fig. 2 is a schematic circuit of an oscillatormodulator system with its associate transmission apparatus.

Referring specifically to Fig. 1, a photocell-amplifier 5 is shown contained within an evacuated envelope 6, the elements of which are a light sensitive cathode 7, a thermionic filament 8, a thermionic control element 9, and a thermionic anode 10. The cathode 7 is photo-active only anteriorly, and is large enough to obscure variations of thermionic light and heat waves. The anode 10 may also enclose the other elements of the device 5 with an opening to permit light reaching the cathode '7. The filament 8 is energized from a source of potential 12, while the potential supply 13 is used for the cathode 7. The plate of the amplifier 5 is energized from a source of potential 14. A light ray may be focussed by a lens 16 on the light active cathode '7 through a window 1'7 of the envelope 6.

The output of the photocell-amplifier 5 is transmitted through an output transformer 20 into delay circuits 21, 22 and 23, after which it is amplified in vacuum tube amplifiers 24, 25 and 26, respectively. These amplifiers are of the type well known in the art with tuned plate circuits having variable capacities as shown at 28, 29 and 30, respectively. The delay circuits 21, 22 and 23 are also variable, and are mechanically associated with the tuneable elements 28, 29 and 30, so that when an amplifier is adjusted for a particular frequency output desired, the delay circuit is adjusted accordingly, in order to create the proper oscillating period within the particular circuit. Of course. these elements may be tuned separately, although unicontrol is preferable. The amplifiers are biased with the sources of potential 32. 33 and 34 obtained through a series of resistance elements 35, 36 and 37. The anodes are energized from potential sources 39, 40 and 41. while the filaments are energized from sources 42, 43 and 44.

The outputs of the three amplifiers are transmitted through output transformers 46, 4! and s, these transformers having third windings so, 5

10 system operates independently of one another;'

51 and 52, from which current may be obtained to supply modulator systems, transmitters or the like. The other secondary windings of the output transformers are connected to light 5 sources in the form of lamps 57, 58 and 59, which may be neon or incandescent. The light rays from these sources are focussed through the lens 16 on the photosensitive element 7 in the envelope 6. Each circuit of the above descr.bed

the various amplifiers being tuned to the particular frequency desired from any particular circuit. The delay circuits further serve as filters for obtaining the desired frequency, since 15 the operation of the oscillator is dependent upon the delay obtained between the creation of the light impulse and the result thereof returning to the light source. Of course, either circuit may be operated singly or any two may be op- 20 erated together, according to the frequencies desired. Any one of sources 57, 58 and 59 may be modulated by another light source 78 focused on the cell 5. The light source 78 receives its energy from a si oe 75 of any ell "ITT'The modulated currents may be transmitted through transmitters 46, 47 or 48.

In Fig. 2 a modulator-oscillator system is shown wherein the device 5 of Fig. 1 is employed 3 with the same focussing lens 16 and potential supply sources 12, 13 and 14. In this particular system a three winding output transformer 60 is used, wherein a third winding 61 is connected with a transmitting system 62 for space trans- 35 mission over an antenna 63 or wire transmission over conductors 64. In the present system one of the amplifiers of Fig. 1 is shown in the block 65, while the delay circuit is shown in the form of a piezoelectric crystal 67, which may have a 40 fixed value of delay, depending upon the frequency of oscillations desired. The output of the amplifier is transmitted through an output transformer 69, the circuits of which may be tuned by variable capacity elements 70 and 71.

45 A light source 73 produces the light waves for impression upon the photosensitive element 7.

This system, so far as the generation of osclllations is concerned, operates in identically the same manner as the system of Fig. 1, that is, a

60 variation in light rays from the source 73 im- 60 from different sou rges such-as the. microphone 75 or television apparatus 76. After amplification by the amplifier 77, the signaling variations are impressed upon the modulating light source 78 which is focussed upon the light sensitive ele- 66 ment 7 of the device 5. With the impression of the second oscillations in the form of light variations upon the sensitive element 7, together with the generated light variation from the source 73, difierential voltages are produced in 70 the device 5, which may be impressed upon the transmitter 62 for broadcasting or direct transmission.

Particular advantages of the above oscillatormodulator are that modulation occurs without 75 distortion, inasmuch as there is no 13 .12.: dens t curve to be considered in the light system, or any limitations on the amplitude thereof except for the constants of the electrical circuit which may be increased in size as desired. Furthermore, the compound oscillating system, such as shown in Fig. 1, may be employed, and all generated frequencies modulated within the same.- system from various sources in accordance with the method and manner disclosed in Fig. 2. It is obvious that a minimum of apparatus is required for 100% modulation of a considerable number of signals on different carrier frequencies.

Although the invention has been described in two of its preferred embodiments, it is to be understood that there are many other systems which may involve the principles of this invention, and which are contemplated to be within the scope of the appended claims.

What is claimed is: v

1. In an electrical oscillating system, a photocell device, a plurality of light sources for actuating said cell, and respective electrical circuits connecting said photocell and said light sources, said electrical circuits having therein current delay devices of different values for energizing said light sources definite time intervals after the actuation of said photocell in accordance with the frequency of the currents impressed thereon, to generate a plurality of alternating currents of different frequencies.

2. In an electrical oscillating system, a light sensitive device, a plurality of sources of light for actuating said device, respective electrical amplifiers for actuating said light sources, said amplifiers being actuated in turn by said photocell and selective delay circuits for coupling said amplifiers to said light sensitive device, said amplifiers energizing said light sources definitetime intervals after actuation of said device in accordance with frequencies impressed thereon.

3. In an electrical oscillating system, a plurality of light sources, electrical circuits for energizing said light sources, respective means within said electrical circuits for energizing each of said light sources at a different period, a light sensitive device actuated by all of said light sources, and means for impressing the electrical variations generated by said device on said electrical circuits, said variations being impressed upon said light sources at time intervals thereafter determined by the frequencies of said vibrations.

4. In an oscillator-modulator device, a plurality of light sources, a light sensitive device actuated by said light sources, a circuit interconnecting one of said light sources and said device for energizing said one light source, means in said circuit for delaying the transmission therethrough of said energizing currents, a definite time interval after the actuation of said device, to produce a continuous oscillating current. and signalling means for energizing said second light source at a different frequency from said oscillating current.

5. In an oscillating system, a light sensitive device, a plurality of light sources, means connecting the output circuit of said device and said sources and cooperating therewith for producing oscillating currents having different frequencies, said means including means for segregating said different frequencies generated and delaying each of said frequencies for different time intervals during transmission between said device and said light sources, and respective amplifying systems {or energizing said light sources individually.

6. In an electrical transmission circuit, a photoelectric cell, electrical amplifying circuits for amplifying currents generated in said cell in accordance with the frequencies thereof, means for producing a plurality of light rays with the outputs of said amplifiers, said light rays being focused upon an element of said photoelectric cell, means for varying the intensity one of said light rays with signals to be transmitted, means located in said amplifier circuits for delaying the transmission of the output currents of said cell to said light producing means definite time intervals in accordance with the frequencies of the current impressed thereon, and means coupled to the output circuit of said amplifiers for transmitting modulateddighj smnalgjp a receiving. station.

'7. In an electrical system for the production of oscillations, means for producing a plurality of light impulses, a corresponding plurality of vacuum tube amplifier circuits, energy for said light impulses being derived from said vacuum tube amplifier circuits, current delay circuits in said amplifier circuits for shifting the phase of the currents through said amplifier circuits' in accordance with the frequencies of the currents impressed thereon, a light sensitive device actuated by said light impulses, said device amplifying the generated currents within said cell, and means for impressing the output of said cell upon said phase shifting circuits.

8. The method of producing electrical variations in current and voltage with a light-to-current translator and a current-to-light translator, comprising actuating each of said translators with the output of the other of said translators and variably dephasing the output of said light-tocurrent translator before it actuates said current- .to-light translator thereby changing the time of actuation of said translators and varying the frequency of the current produced.

9. The method of producing a plurality of electrical variations in current and voltage with a light-to-current translator and a plurality of current-to-light translators, comprising actuating each of said current-to-light translators with the output or said light-to-current translator and actuating said light-to-current translator with the outputs of said plurality of current-to-light translators and varying the periods said ourrent-to-light translators are actuated after actuation of said light-to-current translator.

ALEXANDER. McLEAN NICOLSON. 

